Method for producing smooth galvanized sheet

Claim 1

A PROCESS FOR PRODUCING FLAT GALVANIZED FERROUS STRIP HAVING A UNIFORM, SMOOTH, NON-SPANGLED, LIGHT GRAY SURFACE COATING, SAID PROCESS COMPRISING THE STEPS OF: IMMERSING A FLAT FERROUS BASE STRIP, WITH EACH SURFACE FREE OF OXIDES AND OTHER IMPURITIES AND HAVING A STRIP TEMPERATURE BELOW 900*F., INTO A BATH OF MOLTEN ZINC CONTAINING TRACES OF ALUMINUM; COATING EACH SURFACE OF SAID BASE STRIP WITH THE SAME THICKNESS OF SAID ZINC, BETWEEN 0.1 AND 1.0 OUNCE PER SQUARE FOOT OF SAID ZINC; CONTROLLING THE VARIATION IN SAID ZINC COATING ON A SURFACE, FROM SIDE TO SIDE AND FROM FRONT EDGE TO REAR EDGE OF THE STRIP, TO $.05 OUNCE PER SQUARE FOOT; HEATING THE COATED STRIP, AT A STRIP HEATING RATE OF 25*30*F. PER SECOND, TO A MAXIMUM STRIP TEMPERATURE BETWEEN 1000*-1100*F. TO PROMOTE THE DIFFUSION OF IRON FROM SAID FERROUS BASE STRIP INTO SAID COATING; COOLING SAID STRIP IMMEDIATELY UPON ATTAINMENT OF SAID MAXIMUM STRIP TEMPERATURE, WITHOUT HOLDING AT SAID MAXIMUM STRIP TEMPERATURE, TO A STRIP TEMPERATURE OF 800*F.; CONTROLLING THE COOLING RATE, BETWEEN SAID MAXIMUM STRIP TEMPERATURE AND 800*F., TO DIFFUSE IRON FROM SAID FLAT FERROUS BASE STRIP INTO THE COATING IN AN AMOUNT OF IRON BETWEEN 4 AND 7% OF THE FINAL COATING WEIGHT; AND THEN COOLING SAID STRIP UPON ATTAINMENT OF SAID 800*F. TO A TEMPERATURE BELOW 800*F. AT A COOLING RATE SUFFICIENT TO PREVENT FURTHER DIFFUSION OF IRON INTO SAID COATING.